United Kingdom, Sept. 14 -- Kaley Cuoco felt like she'd lost her own father when John Ritter died.

The Big Bang Theory star worked with Ritter on family sitcom 8 Simple Rules playing his onscreen daughter and she was left devastated when the actor passed away on September 11, 2003 after suffering an aortic dissection on the set of the show.

Kaley attended the John Ritter Foundation for Aortic Health's annual Evening From the Heart Gala in Los Angeles on Saturday night (12.09.26) and she fought back tears as she spoke about her affection for the late actor. She told the audience: "I always cry when I talk about him ...

"When he passed away, I don't want to get dramatic, but I can truly say that was one of the worst days of my life.

'I ...